Preliminary findings by U.S. researchers suggest children born during the COVID-19 pandemic show lower IQ scores than those who were born before January 2020, but the underlying causes are still unknown.

It may be due to the first 1,000 days of a child’s life being the most crucial to development.

The findings were posted in medRxiv ahead of peer review on Aug. 11, stemming from a survey among roughly 605 children in Rhode Island, most of them White, including 39 born in 2018 and 2019.

Environmental factors, including maternal mental and physical health, nutrition, stimulation and supportive caregiving can alter the child’s development.

A Rhode Island study shows that children born during the pandemic had lower IQ's than those who were born before. (iStock)

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The study of pre-pandemic babies shows that they had an IQ ranging from 98.5 to 107.3.

But the IQs of babies born during the pandemic sharply fell 27 to 37 points.

The study attributed lockdown policies aimed at slowing the spread of COVID-19 such as economic shutdowns, mask-wearing, school disruptions, social distancing and stay-at-home orders.

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Because of this, children born after January 2020 from lower socio-economic backgrounds who were hit the hardest during the pandemic (mostly Black and Brown children) had a steeper dip in IQ scores than White children did on average.

"While socio-economic factors appear to mitigate against the negative consequences of the pandemic, the primary factors underlying our observed trends remain unknown," study authors wrote.

However, they suggested potential factors could include shuttered child care and changing workplace environments in influencing children's cognitive development.

Children of mothers with collegiate and post-graduate degrees were less likely to suffer the negative impact of being born during the pandemic.

Research suggests that this could be due to family or social support that can contribute to maternal well-being, which can affect infant temperament, behavior and cognitive development. 

The study also shows more male children were affected than females.

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Maternal stress, both prenatal and post-delivery, added additional effects to the child's development, although there were no drastic increases or decreases to the stress.

Children born before the pandemic did not show any significantly lower verbal, non-verbal and cognitive scores when following the later stages of development through the pandemic, showing that the pandemic hinders mostly early child development.

Researchers are still trying to figure out whether or not these declines are temporal and will normalize once life returns to pre-pandemic times, or if the declines have be a long-lasting effect.